/**
 * @param {number[]} nums
 * @return {number[]}
 */
 var findDisappearedNumbers = function(nums) {
    let length=nums.length;
    let set=new Set();
    let res=[];
    for(num of nums){
        set.add(num);
    }
    for(let i=1;i<=length;i++){
        if(!set.has(i)){
            res.push(i);
        }
    }
    return res;
};